WO2020048281A1 - Pixel circuit and driving method therefor, and display device - Google Patents

Abstract

A pixel circuit and a driving method therefor, and a display device. The pixel circuit comprises an input subcircuit (21), a light-emission control subcircuit (22) and an organic light-emitting transistor (OLET, 1). The input subcircuit (21) is connected to a gate line (Gate), a data line (Data) and the light-emission control subcircuit (22), and is used to write a data signal (V_Data) provided by the data line (Data) to the light-emission control subcircuit (22) under control of a gate scanning signal (V_Gate) provided at the gate line (Gate). The light-emission control subcircuit (22) is connected to a control electrode of the organic light-emitting transistor (OLET, 1), and is used to control, according to the data signal (V_Data) written thereto, a voltage at the control electrode of the organic light-emitting transistor (OLET, 1) so as to drive the organic light-emitting transistor (OLET, 1) to emit light. The invention enables active matrix driving to be performed on an organic light-emitting transistor (OLET, 1) applied in a display device.

Description

Pixel circuit, driving method therefor, and display device

Related applications

This application claims the rights and interests of Chinese Patent Application No. 201811039872.3, filed on September 6, 2018, and the contents of the above-mentioned Chinese patent application disclosure are incorporated herein by reference in its entirety as part of this application.

Technical field

The present disclosure relates to the field of display technology, and in particular, to a pixel circuit, a driving method therefor, and a display device.

Background technique

Organic Light Emitting Transistor (OLET) also has the circuit modulation function of the Organic Field-effect Transistor (OFET) and the light emitting function of Organic Light-Emitting Diode (OLED). . In theory, OLET can have higher carrier mobility than OLED, and better luminous efficiency and luminous intensity. It will exist in the fields of flat panel display, optical communication, solid-state lighting, and electric pumped organic lasers. Great application value.

Summary of the Invention

According to a first aspect of an embodiment of the present disclosure, a pixel circuit is provided. The pixel circuit includes an input sub-circuit, a light-emitting control sub-circuit, and an organic light-emitting transistor. The input sub-circuit is connected to a gate line, a data line, and the light emission control sub-circuit, and is configured to write a data signal provided by the data line under the control of a gate scan signal provided by the gate line. The light emission control sub-circuit. The light emission control sub-circuit is connected to a control electrode of the organic light emitting transistor, and is configured to control a voltage of the control electrode of the organic light emitting transistor according to the written data signal to drive the organic light emitting transistor to emit light.

Optionally, the first electrode of the organic light emitting transistor is connected to a second voltage terminal, and is configured to emit light under the driving of a driving current corresponding to the data signal and a second voltage signal provided by the second voltage terminal.

Optionally, the pixel circuit further includes a light-emitting cut-off sub-circuit. The light emitting cut-off circuit is connected to a pulse width modulation signal line and a control electrode of the organic light emitting transistor, and is configured to control the organic light emitting transistor to stop emitting light according to a pulse width modulation signal provided by the pulse width modulation signal line. The duty cycle of the pulse width modulation signal is determined according to the gray scale to be displayed by the pixel circuit.

Optionally, the voltage of the data signal is a gate voltage when the light emitting intensity of the organic light emitting transistor is maximum.

Optionally, the light-emitting cut-off sub-circuit includes a first transistor. The control electrode of the first transistor is connected to the PWM signal line, the first electrode of the first transistor is connected to a third voltage terminal, and the second electrode of the first transistor is connected to the organic light emitting transistor. Control pole connection. The first transistor is configured to be turned on when the pulse width modulation signal is at an active level to control the organic by applying a third voltage signal provided by a third voltage terminal to a control electrode of the organic light emitting transistor. The light emitting transistor stops emitting light.

Optionally, the first voltage terminal is connected to the second voltage terminal.

Optionally, the organic light emitting transistor is a bipolar organic light emitting transistor. The second voltage terminal is configured to provide an AC voltage signal as the second voltage signal.

Optionally, the second voltage terminal is configured to alternately provide a positive-polarity voltage signal and a negative-polarity voltage signal once every two consecutive frames in a frame period.

Optionally, the input sub-circuit includes a second transistor. A control electrode of the second transistor is connected to the gate line, a first electrode of the second transistor is connected to the data line, and a second electrode of the second transistor is connected to the light emission control sub-circuit.

Optionally, the light emission control sub-circuit includes a storage capacitor. A first pole of the storage capacitor is connected to the first voltage terminal, and a second pole of the storage capacitor is connected to a control electrode of the organic light emitting transistor and an output terminal of the input sub-circuit.

Optionally, the second voltage terminal includes a power voltage terminal. The second electrode of the organic light emitting transistor is connected to a common voltage terminal.

According to a second aspect of the embodiments of the present disclosure, a driving method for a pixel circuit is provided. The pixel circuit includes an input sub-circuit, a light-emitting control sub-circuit, and an organic light-emitting transistor. The driving method includes: during a frame time for a frame to be displayed: during the data writing phase, the input sub-circuit controls the data signal provided by the data line under the control of the gate scan signal provided by the gate line Write the light-emitting control sub-circuit; and in the light-emitting phase, the light-emitting control sub-circuit drives the organic light-emitting field-effect tube to emit light according to the written data signal.

Optionally, writing the data signal provided by the data line into the light-emitting control sub-circuit includes: holding the data signal at the control electrode of the organic light-emitting transistor by supplying a first voltage signal to the light-emitting control sub-circuit. Control voltage corresponding to the signal. The controlling the light emitting of the organic light emitting transistor by the light emitting control sub-circuit according to the written data signal includes: providing a second voltage signal to a first pole of the organic light emitting transistor, and by corresponding to the data signal and the data signal. A driving current of a second voltage signal drives the organic light emitting transistor to emit light.

Optionally, the voltage of the data signal is determined according to a gray scale to be displayed by the pixel circuit.

Optionally, the one-frame time further includes a light-off cut-off phase. The driving method further includes controlling the organic light emitting transistor to stop emitting light by applying a third voltage signal to a control electrode of the organic light emitting transistor in the light emission off stage. The duration of the light-emitting phase is determined according to the gray scale of the pixels or sub-pixels of the frame to be displayed.

Optionally, the voltage of the data signal is a control electrode voltage corresponding to when the light emitting intensity of the organic light emitting transistor is maximum.

Optionally, the organic light emitting transistor is a bipolar organic light emitting transistor, and the second voltage signal is an alternating voltage signal.

Optionally, a positive polarity voltage signal and a negative polarity voltage signal are alternately applied to the first pole of the organic light emitting transistor in a frame period in every two consecutive frame times.

According to a third aspect of the embodiments of the present disclosure, a display device is provided. The display device includes a pixel circuit as described above.

According to a fourth aspect of the embodiments of the present disclosure, a signal processor is provided. The signal processor is applied to a pixel circuit including a light-emitting cut-off sub-circuit as described above. The signal processor is configured to calculate a duty cycle of a pulse width modulation signal according to a gray level to be displayed by the pixel circuit, generate a corresponding pulse width modulation signal, and output the corresponding pulse width modulation signal to a light-emitting cut-off sub-circuit in the pixel circuit. .

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present disclosure will become more apparent when specific embodiments are described in detail with reference to the drawings. In the drawings:

FIG. 1 is a schematic structural diagram of OLET;

Figure 2 is a working state diagram of OLET under different voltages;

3 is a characteristic diagram of carrier transfer in OLET;

FIG. 4 is an output characteristic diagram of carriers in OLET;

FIG. 5 is a schematic diagram of carrier transfer in the state ② of OLET shown in FIG. 2; FIG.

FIG. 6 is a schematic diagram of carrier transfer in the state ⑤ of the OLET shown in FIG. 2; FIG.

7 is a schematic structural diagram of a pixel circuit according to an embodiment of the present disclosure;

8 is a timing control diagram of the pixel circuit shown in FIG. 7;

9 is a schematic structural diagram of another pixel circuit according to an embodiment of the present disclosure;

10 is a timing control diagram of the pixel circuit shown in FIG. 9;

11 is a schematic structural diagram of still another pixel circuit according to an embodiment of the present disclosure;

FIG. 12 is a timing control diagram of the pixel circuit shown in FIG. 11.

detailed description

In order to facilitate understanding, the pixel circuit, the driving method, and the display device provided by the embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

The organic light emitting transistor has both a circuit modulation function of an airport effect transistor and a light emitting function of an organic light emitting diode. OLET is a heterojunction bipolar device, and one of its typical structures is shown in FIG. 1. As shown in FIG. 1, OLET 1 includes a gate electrode 10, an electron transport layer 14, a hole transport layer 15, and a source electrode 16 and a drain electrode 17 provided on the surface of the hole transport layer 15, which are sequentially stacked in the light emitting direction. The gate electrode 10 is generally composed of an aluminum conductive layer 11, an N-type silicon conductive layer 12, and a silicon dioxide layer 13 which are sequentially stacked.

Figure 2 shows the working state diagram of OLET under different voltages. Taking OLET1 in FIG. 1 as an example, it can adjust carriers or electrons through the bias voltage V _GS between its gate 10 and source 16 and the lateral electric field V _DS between source 16 and drain 17. And hole injection barriers, and correspondingly control the injection amount of electrons and holes, so that carriers injected into the electron transport layer 14 and the hole transport layer 15 can form a channel current under the action of the lateral electric field V _DS . According to the application of the bias voltage V _GS and the lateral electric field V _DS in OLET, OLET can usually work in the six states ①-⑥ as shown in FIG. 2, where V _TH is the threshold voltage that makes OLET on.

State ①, when V _GS -V _TH > 0, electrons can be injected from the source 16 overcoming the injection barrier; while V _DS <V _GS -V _TH , holes cannot be injected from the drain 17 overcoming the injection barrier. The electrons thus injected move toward the drain electrode 17 under the action of the lateral electric field V _DS and are collected by the drain electrode 17. OLET is in an electron-transporting state, and the channel current of OLET mainly manifests as an electron current.

State ②, as V _DS increases to positive polarity, the hole injection barrier gradually decreases. After the holes are injected from the drain electrode 17 against the injection barrier, the holes can also move toward the source electrode 16 under the action of the lateral electric field V _DS and be collected by the source electrode 16. In this way, OLET is in a state in which electrons and holes are transported simultaneously, and the channel current of OLET is mainly expressed as the sum of the electron current and the hole current.

State ③, when V _GS -V _TH &lt; 0 and V _DS &gt; 0, electrons cannot be injected from the source 16 against the injection barrier, and holes can be injected from the drain 17 against the injection barrier. The injected hole moves to the source 16 under the action of the lateral electric field V _DS and is collected by the source 16. OLET is in a hole-transporting state, and the channel current of OLET is mainly a hole current.

State ④, as V _DS increases to the negative polarity, the injection barrier of holes at the drain 17 gradually increases, and the number of holes injected from the drain 17 to overcome the injection barrier gradually decreases. When V _DS <0, the lateral electric field V _DS between the source 16 and the drain 17 changes in the opposite direction, and holes will be injected from the source 16 and collected by the drain 17. In this way, OLET is still in the state of hole transport, and the channel current of OLET mainly manifests as hole current.

State ⑤, when V _DS is further increased to a negative polarity to an absolute value greater than (V _GS -V _TH ), electrons can be injected from the drain 17 overcoming the injection barrier, and the electrons can also be directed by the lateral electric field V _DS The source electrode 16 moves and is collected by the source electrode 16. In this way, OLET is in a state in which electrons and holes are transported simultaneously, and the channel current of OLET is mainly expressed as the sum of the electron current and the hole current.

State ⑥, when V _GS -V _TH > 0 and V _DS <0, only electrons can be injected from the drain 17 and collected by the source 16 over the injection barrier. In this way, OLET is in the state of electron transmission, and the channel current of OLET mainly manifests as electron current.

FIG. 3 shows the transfer characteristics of the carriers in the bipolar OLET, and FIG. 4 shows the output characteristics of the carriers in the bipolar OLET. It can be seen from FIG. 3 and FIG. 4 that as the OLET bias voltage V _GS and the lateral electric field V _DS change, the carrier injection barrier in OLET also changes accordingly. Therefore, the injection of electrons and holes in OLET will constantly change, and there will be no state where electrons or holes are completely blocked. That is to say, the channel current of OLET will always appear as the sum of the electron current and the hole current, but the electron current and the hole current will show a relative change in size, that is, the electron current or the hole may The current is the main current.

Relevant technologies have given different channel current calculation formulas for each of the above-mentioned working states of OLET. For details, please refer to "Electron and Ambipolar Transport in Organic Field-Effect Transistors, Chemical Reviews, 2007, 107 (4): 1296-1323. ". In these related technologies, it is assumed that the carrier mobility in OLET depends on the gate voltage, and according to the application of bias V _GS and lateral electric field V _DS in OLET, the six working states of OLET can be divided into : Unipolar linear region, unipolar saturation region, and bipolar region. The unipolar linear region refers to a region where the channel current is mainly an electron current or a hole current, and the channel current changes linearly. The unipolar saturation region refers to a region where the channel current is mainly an electron current or a hole current, and the channel current is in a saturated state. A bipolar region refers to a region in which an electron current and a hole current coexist.

Since OLET usually adopts a heterojunction bipolar structure, its normal light emission needs to work in the bipolar region, that is, the state ② and the state ⑤ shown in FIG. 2, that is, a region in which an electron current and a hole current coexist.

Figures 5 and 6 show the carrier transport path after the source and drain are connected to AC when the source and drain of OLET are symmetrical. The carrier transmission path of OLET shown in state ② is shown in FIG. 5, and the carrier transmission path of OLET shown in state ⑤ is shown in FIG. 6. Assuming that the hole injection barrier voltage V _{TH-h of the} OLET is less than the electron injection barrier voltage V _Th-e , then when V _GS > V _Th-e and (V _GS -V _TH-h ) ≤V _DS ≤ (V _GS -V _TH-e ); or | V _GS | ＞ | V _Th-e | and (V _GS -V _TH-h ) ≤V _DS ≤ (V _GS -V _TH-e ), the channel of OLET The current I _DS includes two parts: an electron current I _DS-e and a hole current I _DS-h , namely:

Electron current | I _DS-e | = WC _i / (2L) [μ _e (V _GS -V _TH-e ) ² ] (1);

Hole current | I _DS-h | = WC _i / (2L) [μ _h (V _DS- (V _GS -V _TH-h )) ² ] (2);

Channel current | I _DS | = WC _i / (2L) [μ _e (V _GS -V _TH-e ) ² + μ _h (V _DS- (V _GS -V _TH-h )) ² ] (3);

Among them, W is the channel width of OLET, C _i is the unit gate capacitance of OLET, L is the channel length of OLET, μ _e is the electron mobility of OLET, and μ _h is the hole mobility of OLET.

FIG. 7 illustrates a pixel circuit provided according to an embodiment of the present disclosure. The pixel circuit includes an input sub-circuit 21, a light emission control sub-circuit 22, and OLET 1. The input sub-circuit 21 is connected to the gate line Gate, the data line Data, and the light emission control sub-circuit 22, and is used for controlling the data signal V _Data provided by the data line Data under the control of the gate scan signal V _Gate provided by the gate line Gate. Write the light emission control sub-circuit 22. The light emission control sub-circuit 22 is connected to the control electrode of OLET 1 and is used to control the voltage of the control electrode of the organic light emitting transistor to drive the organic light emitting transistor to emit light according to the written data signal.

In some embodiments, the light emission control sub-circuit 22 has a first terminal connected to the first voltage terminal, and a second terminal connected to the output terminal of the input sub-circuit 21 and the control electrode of OLET1 for passing the first voltage. The first voltage signal provided by the terminal maintains a gate voltage corresponding to the data signal at the gate of the organic light emitting transistor. Exemplarily, the light emission control sub-circuit 22 is configured to receive a data signal output from the input sub-circuit 21 at a second end of the pixel circuit when the pixel is scanned by the gate scan signal, and the pixel circuit is not selected when the gate scan signal is located At this time, the data signal is held at the gate of OLET1 to provide a gate voltage corresponding to the data signal. The first pole of OLET1 is connected to a second voltage terminal, and is configured to emit light under the driving of a driving current corresponding to the data signal and a second voltage signal provided by the second voltage terminal. It can be understood that the magnitude of the driving current of OLET1 depends on the control electrode voltage of its control electrode and the second voltage provided by the second voltage terminal of the first electrode. The light emission intensity of OLET1 can vary with the driving current. In some embodiments, the voltage of the data signal is determined according to a gray scale to be displayed by the pixel circuit. It can be understood that the gray scale to be displayed by the pixel circuit is determined based on the gray scale of an image pixel (including a sub-pixel) corresponding to the pixel circuit in an image frame to be displayed.

The gate of OLET 1 usually refers to the gate of OLET 1. OLET 1 further includes a second pole disposed corresponding to the first pole. When the first pole is the source, the second pole is the drain. When its first pole is drain, its second pole is source. In this embodiment, the first pole of OLET 1 is connected to the second voltage terminal. The second voltage terminal may be a power voltage terminal, which is used to provide a power voltage signal V _DD as a second voltage signal. The second pole of OLET 1 can be connected to a common voltage terminal. The common voltage terminal is used to provide a common voltage signal Vss. When the light emission control sub-circuit 22 controls the light emission of OLET 1 according to the data signal, OLET 1 can emit light under the driving of the data signal V _Data and the power supply voltage signal V _DD . Generally, the potential of Vss is smaller than the potential of V _DD . For example, Vss may be low and V _DD is high.

Optionally, the input sub-circuit 21 includes a second transistor T ₂ . The control electrode of the second transistor T ₂ is connected to the gate line Gate, the first electrode of the second transistor T ₂ is connected to the data line Data, and the second electrode of the second transistor T ₂ is connected to the light-emitting control sub-circuit 22 as its output terminal, for example. . The second transistor T2 is configured to be turned on when a gate scan signal is addressed to the pixel circuit, that is, when the gate scan signal is at an active level, so as to output a data signal V _Data to the light emission control sub-circuit 22. The second transistor T2 is also configured to be turned off when the gate scan signal is not addressed to the pixel circuit, that is, when the gate scan signal is at an inactive level. The second transistor T2 may be an N-type or a P-type transistor. Exemplarily, the second transistor T ₂ may be a P-type transistor.

Optionally, the light emission control sub-circuit 22 includes a storage capacitor C. The first pole of the storage capacitor C is connected to the first voltage terminal, and the second pole of the storage capacitor C is connected to the control electrode of OLET1 and the output terminal of the input sub-circuit 21. The storage capacitor C is configured to receive a data signal at a second pole of the pixel circuit when the gate scan signal is addressed to the pixel circuit and charge the first voltage signal input through the first voltage terminal, so that when the gate scan signal is not selected, When the pixel circuit is accessed, the data signal is kept on the control electrode of OLET1.

In some embodiments, the first voltage terminal may be connected to the second voltage terminal, that is, the first voltage terminal and the second voltage terminal may be configured to provide the same voltage signal, such as the power supply voltage signal V _DD shown in FIG. 7. Alternatively, the first voltage terminal and the second voltage terminal may be configured to provide different voltage signals. For example, the first voltage terminal may be configured to provide a common voltage signal Vss, and the second voltage terminal may be configured to provide a power voltage signal V _DD . The voltage signals provided by the first voltage terminal and the second voltage terminal can be set according to actual needs, but are not limited thereto.

The embodiments of the present disclosure provide a pixel circuit based on the light emitting principle of OLET, so that when OLET is applied to a display device, OLET is actively driven. The pixel circuit can use the input sub-circuit 21 to write the data signal V _Data provided by the data line _Data to the light-emitting control sub-unit under the control of the gate scan signal V _Gate provided by the gate line Gate when the address OLET 1 is selected. Circuit 22. Then, the light emission control sub-circuit 22 controls the light emission of OLET 1 based on the written data signal V _Data . In one example, the light emission control sub-circuit 22 maintains the voltage of the control electrode of OLET 1 at the on-voltage according to the written data signal V _Data, that is, the voltage that makes OLET 1 conductive. For example, the voltage of the written data signal V _Data can be set to be equal to the on-voltage. In this way, OLET 1 can drive the data signal V _Data and the second voltage signal provided by the second voltage terminal to form a conducting current (ie, a driving current) between the first pole and the second pole of the data signal. Illuminated display. The light-emission time of OLET 1 depends on the time that the light-emission control sub-circuit 22 maintains the voltage of the control electrode of OLET 1 at the on-voltage.

It should be noted that combined with the above formula for calculating the channel current in OLET, it can be known that the luminous intensity of OLET usually depends on the combined current of its electron current and hole current, that is, the luminous intensity L of OLET and the minimum electron current | I _{DS- e} | or hole current | I _DS-h | Returning to FIG. 4, it can be seen from the figure that the interval of V _DS > 0 is taken as an example. If V _DS remains constant, when the gate voltage V _g (eg, V _Data ) of OLET is in the bipolar region, When it becomes small, the electron current I _DS-e will gradually increase, and the hole current I _{DS-h will} gradually decrease. Therefore, if you want to obtain the maximum luminous intensity of OLET 1, you need to control the electron current | I _DS-e | of OLET equal to its hole current | I _DS-h |, that is:

WC _i / (2L) [μ _e (V _GS -V _TH-e ) ² ] = WC _i / (2L) [μ _h (V _DS- (V _GS -V _TH-h )) ² ] (4).

Taking the pixel circuit shown in FIG. 7 as an example, the first pole of OLET 1 is connected to a second voltage terminal, and the second voltage terminal is a power voltage terminal for providing a power voltage signal V _DD . The second pole of OLET 1 is connected to a common voltage terminal, and the common voltage terminal is used to provide a common voltage signal V _SS . Assuming that the common voltage terminal is grounded, that is, when the voltage of the second pole of OLET 1 is 0V, it can be determined by calculating equation (4):

Among them, Vgm is the control electrode driving voltage corresponding to the maximum luminous intensity of OLET 1, which can be provided by the data signal V _Data transmitted by the data line Data; Vs is the voltage of the first pole of OLET 1, which can be transmitted by the power supply voltage signal. Provided by V _DD ; V _TH-e is the electron injection barrier voltage of OLET 1, V _TH-h is the hole injection barrier voltage of OLET 1, μ _e is the electron mobility of OLET 1, and μ _h is the vacancy of OLET 1. Acuity mobility.

Therefore, when the data signal V _Data ∈ (0, Vgm) provided by the data line Data, the light emission control sub-circuit 22 controls the light emission intensity of OLET 1 according to the written data signal V _Data , and the light emission intensity will vary with V _Data Increases monotonically. When V _Data > Vgm, the light emission control sub-circuit 22 controls the light emission intensity of OLET 1 according to the written data signal V _Data , and the light emission intensity will decrease as V _Data increases.

When the pixel circuit provided by the embodiment of the present disclosure is in use, the data signal V _{Data of} the data line Data thereof may be determined according to the gray scale of the pixel or sub-pixel of the frame to be displayed. In this way, according to the size of the data signal V _Data provided by the data line Data, the light emission control sub-circuit 22 can simultaneously control the light emission of OLET 1 while controlling the size of the light emission current of OLET 1, that is, synchronously control the light emission intensity of OLET 1, thereby controlling Gray scale to be displayed in OLET 1.

FIG. 8 illustrates a driving timing chart for OLET according to an embodiment of the present disclosure. In FIG. 8, a frame time T of a frame to be displayed includes a data writing phase t ₁ and a light emitting phase t ₂ . The driving method for the pixel circuit will be described below with reference to FIGS. 7 and 8. The driving method includes:

In the data writing stage t ₁ , the input sub-circuit 21 writes the data signal V _Data provided by the data line _Data into the light emission control sub-circuit 22 under the control of the gate scan signal V _Gate provided by the gate line Gate. Exemplarily, a control electrode voltage corresponding to the data signal may be maintained at a control electrode of the organic light emitting transistor by supplying a first voltage signal to the light emission control sub-circuit.

In the light emitting period t ₂ , the light emitting control sub-circuit 22 drives the OLET 1 to emit light according to the written data signal V _Data . Exemplarily, a second voltage signal may be provided to a first electrode of the organic light emitting transistor, and the organic light may be driven by a driving current corresponding to the data signal and a second voltage signal provided by the second voltage terminal. The light emitting transistor emits light. The data signal is determined according to a gray scale to be displayed by the pixel circuit.

In some embodiments, it is assumed that in the pixel circuit shown in FIG. 7, the input sub-circuit 21 includes a second transistor T ₂ , which is a P-type transistor and is turned on at a low level; and the light-emitting control sub-circuit 22 includes a storage capacitor. C, whose first pole is connected to the power voltage terminal V _DD .

In the data writing stage t ₁ , the gate line Gate provides a low-level gate scan signal V _Gate , so that the second transistor T _{2 is} turned on, and the data signal V _Data on the data line Data is output to the second of the storage capacitor C. pole. Optionally, the data line Data may provide a low-level data signal V _Data during the t ₁ phase. The storage capacitor C is charged by the data signal V _Data and the power supply voltage signal V _DD to write the data signal V _Data .

In the light emitting period t ₂ , the gate line Gate provides a high-level scanning signal V _Gate , so that the second transistor T _{2 is} turned off. Optionally, the data line Data may provide a high-level data signal V _Data . The storage capacitor C is discharged, thereby maintaining the voltage of the control electrode of the OLET 1 at the on-voltage based on the written data signal V _Data . This on-voltage is equal to the voltage V _{Data of} the written data signal. In this way, OLET 1 can drive the data signal V _Data and the second voltage signal provided by the second voltage terminal to form a conducting current between the first electrode and the second electrode to perform light-emitting display. The light-emission time of OLET 1 depends on the time that the storage capacitor C keeps the voltage of the control electrode of OLET 1 at the on-voltage.

In the driving method for a pixel circuit provided by the embodiment of the present disclosure, at a data writing stage t ₁ , an input sub-circuit 21 is used to write a data signal V _Data provided by a data line _Data into a light-emitting control sub-circuit 22, and in a light-emitting stage t _2, the sub-control circuit 22 controls the light emission corresponding to the data signal emission OLET written V _data, the display device can be realized in each of OLET active drive, in order to control the light emitting display OLET each well.

It can be understood that the voltage of the data signal of the data line Data can be determined according to the gray scale of the pixel or sub-pixel to be displayed by the pixel circuit in the frame to be displayed. In this way, during the light emitting period t ₂ , the storage capacitor C can also control the light emitting intensity of OLET 1 according to the written data signal V _Data .

Exemplarily, the control electrode driving voltage Vgm corresponding to the maximum luminous intensity of OLET1 satisfies:

Among them, Vs is the voltage of the first pole of OLET 1; V _TH-e is the electron injection barrier voltage of OLET 1; V _TH-h is the hole injection barrier voltage of OLET 1; μ _e is the electron migration of OLET 1 Rate, μ _h is the hole mobility of OLET 1.

When the data signal V _Data ∈ (0, Vgm) provided by the data line Data, the light emission intensity of OLET 1 controlled by the storage capacitor C according to the written data signal V _Data , and the light emission intensity will be monotonic as V _Data increases When V _Data > Vgm, the light emitting intensity of OLET 1 controlled by the storage capacitor C according to the written data signal V _Data , and the light emitting intensity will decrease as V _Data increases.

Therefore, the driving method provided in the embodiment of the present disclosure determines the data signal V _{Data of the} data line Data according to the gray levels of the sub-pixels of the frame to be displayed, so that the light emission control sub-circuit 22 can control the data signal V _Data according to the magnitude of the data signal V _Data . At the same time as the OLET emits light, it simultaneously controls the size of the light emission current of OLET, that is, synchronously controls the light emission intensity of OLET, thereby controlling the gray level to be displayed by OLET.

In some embodiments, as shown in FIG. 4 above, the output characteristic curve of the bipolar OLET is symmetrical with respect to the y-axis, so the first pole and the second pole of the above-mentioned OLET 1 may have the same structure and function, that is, The first pole of OLET1 can input a positive voltage signal or a negative voltage signal. Of course, when the first pole of OLET1 inputs a positive polarity voltage signal, the second pole of OLET1 needs to input a negative polarity voltage signal; and when the first pole of OLET1 inputs a negative voltage signal, the second pole of OLET1 needs Corresponds to the input positive polarity voltage signal.

Thus, the second voltage terminal connected to the first pole of OLET 1 may be configured to provide an AC voltage signal V _AC as the second voltage signal.

FIG. 9 is a schematic structural diagram of another pixel circuit according to an embodiment of the present disclosure. In this embodiment, the first pole of OLET 1 is connected to a second voltage terminal, and the second voltage terminal is used to provide an AC voltage signal V _AC ; the second pole of OLET 1 is connected to a common voltage terminal, and the common voltage terminal is used for Provide a common voltage signal V _SS .

FIG. 10 shows an exemplary timing control diagram of the pixel circuit shown in FIG. 9. As shown in FIG. 10, the AC voltage signal V _AC may be set to be a positive voltage signal in a first frame time T1 and a negative voltage signal in a second frame time T2, so that in two consecutive frame times A positive polarity signal and a negative polarity signal are respectively input to the first pole of OLET 1 in a frame period. Alternatively, the period in which the AC voltage signal V _{AC is} in the positive polarity and the negative polarity may be set in any suitable manner.

The pixel circuit including the OLET provided by the embodiment of the present disclosure uses the AC voltage signal V _AC as the transmission signal of the second voltage terminal, which can not only directly use the AC voltage provided by the commercial power, avoid AC-DC filtering conversion, but also improve the power utilization rate. It can effectively prevent OLET 1 from aging due to long-term unidirectional movement of its carriers, which is conducive to extending the service life of OLET 1.

FIG. 11 is a schematic structural diagram of another pixel circuit according to an embodiment of the present disclosure. The pixel circuit in FIG. 11 is similar to that shown in FIG. 7 except that the pixel circuit further includes a light-emitting cut-off sub-circuit 23. The light-emitting cut-off sub-circuit 23 is connected to the pulse width modulation signal line PWM, the third voltage terminal and the control electrode of OLET 1. It is used for the pulse width modulation signal (Pulse Width Modulation, PWM for short) provided by the pulse width modulation signal line PWM. Under the control of the MOSFET, the third voltage signal V _int provided by the third voltage terminal is applied to the control electrode of the OLET 1 to control the OLET 1 to be turned off, and thereby stop emitting light. In this embodiment, the duty cycle of the pulse width modulation signal is determined according to the gray scale of a pixel to be displayed by the pixel circuit (ie, OLET 1).

Optionally, the light-emitting cut-off sub-circuit includes a first transistor T ₁ . The control electrode of the first transistor T ₁ is connected to the PWM signal line PWM, the first electrode of the first transistor T ₁ is connected to the third voltage terminal, and the second electrode of the first transistor T ₁ is connected to the control electrode of OLET 1. The first transistor T1 may be an N-type or a P-type transistor. Exemplarily, the first transistor T1 is a P-type transistor. In addition, in order to facilitate the wiring of the pixel circuit, the above-mentioned control electrode of OLET 1, the second electrode of the storage capacitor C, the second electrode of the first transistor T _{1 and} the second electrode of the second transistor T ₂ are connected through the first node N ₁ respectively. .

According to this embodiment of the present disclosure, the light-emitting cut-off sub-circuit 23 can be controlled to stop OLET1 under the control of the corresponding pulse width modulation signal, so as to realize precise control of the duration of the light-emission of OLET within each frame time of the frame to be displayed . By using the light and dark changes of OLET in each frame time in this way, the gray scale to be displayed by OLET can be accurately controlled.

In addition, when the gray level to be displayed by OLET is controlled by using the above-mentioned way of controlling the light emission duration of OLET, the data signal V _Data provided by the data line Data in the pixel circuit does not need to be determined according to the gray level of the sub-pixel of the frame to be displayed. Data signal V _Data data line Data provided may be equal to the luminous intensity OLET gate voltage Vgm at maximum, to ensure OLET balance of electron and hole injection, so as to ensure maximum OLET includes the photoelectric conversion efficiency. Since the light emission intensity of OLET can be controlled at the maximum at all times, the light emission efficiency of OLET is effectively improved.

FIG. 12 is a timing control diagram of the pixel circuit shown in FIG. 11. As shown in FIG. 12, one frame time T of a frame to be displayed is divided into three phases, that is, a data writing phase t ₁ , a light emitting phase t _2, and a light emitting cut-off phase t ₃ . In the data writing stage t ₁ , the input sub-circuit 21 writes the data signal V _Data provided by the data line _Data into the light emission control sub-circuit 22 under the control of the gate scan signal V _Gate provided by the gate line Gate. The data signal V _Data is equal to the control electrode driving voltage Vgm corresponding to the maximum light emission intensity of OLET 1 to ensure that OLET 1 can always maintain the maximum light emission intensity during the light emission period t ₂ .

In the light-emitting phase t ₂ , the light-emitting control sub-circuit 22 outputs the written data signal V _Data , and the second voltage signal terminal outputs a second voltage signal to drive OLET 1 to emit light.

In the light-off period t ₃ , a third voltage signal V _{int is} input to OLET 1 to control OLET 1 to stop emitting light. The duration of the lighting period t ₂ is determined according to the gray scale of the sub-pixels of the frame to be displayed.

In some embodiments, the pixel circuit shown in FIG. 11 is taken as an example to explain as follows: the pixel circuit is provided with a light-emitting cut-off sub-circuit 23. The first transistor T _{1 of the} light-emitting cut-off sub-circuit 23 is a P-type transistor and is turned on at a low level. In the light-off period t ₃ , the PWM signal line PWM outputs a low-level PWM signal, the first transistor T _{1 is} turned on, and the third voltage signal V _int provided by the third voltage terminal is output to the OLET 1 Control pole, control OLET 1 to stop emitting light. The third voltage signal V _int should be the turn-off voltage of OLET 1.

According to the driving method provided in the embodiment of the present disclosure, after determining the light emitting duration corresponding to the lighting period t ₂ of OLET 1 according to the gray level of the sub-pixels of the frame to be displayed, it is possible to precisely control the stopping of light emitting at the light emitting cut-off phase t _{3 of} OLET 1 to realize OLET 1 Light flashes during each frame. Because a frame time is usually less than or equal to 1/60 second, that is, far less than the recognition frequency of the displayed image by the human eye, this embodiment can accurately control OLET 1 by accurately controlling the light and dark flicker of OLET 1 in each frame time. The gray scale to be displayed. Moreover, when the gray level to be displayed by OLET 1 is controlled by using the above-mentioned method of controlling the light emission duration of OLET 1, the data signal V _Data provided by the data line Data in the pixel circuit does not need to be based on the gray level of the sub-pixels of the frame to be displayed. determining a data signal V _data data line data provided may be equal to control 1 OLET emission intensity corresponding to the maximum drive voltage Vgm, OLET 1 to ensure the balance of electron and hole injection, thereby ensuring the maximum OLET 1 includes photoelectric The conversion efficiency, that is, OLET 1 can always maintain the maximum luminous intensity at the light-emitting stage t ₂ , which effectively improves the luminous efficiency of OLET 1.

In some embodiments, in the driving method of OLET provided by the above embodiment, the second voltage signal output from the second voltage signal terminal may be an AC voltage signal. This embodiment uses an AC voltage signal as the second voltage signal, which can not only directly use the AC voltage provided by the commercial power, avoid AC / DC filtering conversion, improve the power utilization rate, but also effectively prevent OLET from long-term unidirectional movement of its carriers. And aging is conducive to extending the service life of OLET.

An embodiment of the present disclosure further provides a display device including the pixel circuit including OLET provided by the foregoing embodiment. The beneficial effects that can be achieved by the display device provided by the embodiments of the present disclosure are the same as the beneficial effects that can be achieved by the pixel circuit provided by the foregoing embodiments, and are not described herein.

The display device provided in the foregoing embodiment may be a product or component having a display function, such as a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, or a navigator.

An embodiment of the present disclosure further provides a signal processor, which is applied to a pixel circuit provided with a light-emitting cut-off sub-circuit in the above embodiment. The signal processor is configured to calculate the duty cycle of the pulse width modulation signal according to the gray level to be displayed by OLET, to generate a corresponding pulse width modulation signal, and output it to the light-emitting cut-off sub-circuit in the pixel circuit. That is, the signal processor provided by the embodiment of the present disclosure can convert a gray scale corresponding to an image pixel into a light emission duration, and adjust the brightness by adjusting the light emission duration of the light emitting unit in the pixel circuit. It can be understood that the signal processor may be implemented by a signal processing integrated chip in the display device.

In the description of the foregoing embodiments, specific features, structures, materials, or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

The above is only a specific implementation of the present disclosure, but the scope of protection of the present disclosure is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present disclosure. It should be covered by the protection scope of this disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims (20)

1. A pixel circuit includes an input sub-circuit, a light-emitting control sub-circuit, and an organic light-emitting transistor;

   The input sub-circuit is connected to a gate line, a data line, and the light emission control sub-circuit, and is configured to write a data signal provided by the data line under the control of a gate scan signal provided by the gate line. The light emission control sub-circuit; and

   The light emission control sub-circuit is connected to a control electrode of the organic light emitting transistor, and is configured to control a voltage of the control electrode of the organic light emitting transistor according to the written data signal to drive the organic light emitting transistor to emit light.
2. The pixel circuit according to claim 1, wherein a first electrode of the organic light emitting transistor is connected to a second voltage terminal, and is configured to correspond to the data signal and a second voltage signal provided by the second voltage terminal. Driven by a driving current.
3. The pixel circuit according to claim 1 or 2, further comprising a light-emitting cut-off sub-circuit;

   The light-emitting cut-off sub-circuit is connected to a pulse width modulation signal line and a control electrode of the organic light emitting transistor, and is configured to control the organic light emitting transistor to stop emitting light according to a pulse width modulation signal provided by the pulse width modulation signal line;

   The duty cycle of the pulse width modulation signal is determined according to a gray scale to be displayed by the pixel circuit.
4. The pixel circuit according to claim 3, wherein a voltage of the data signal is a gate voltage when a light emission intensity of the organic light emitting transistor is maximum.
5. The pixel circuit according to claim 3, wherein the light-emitting off sub-circuit includes a first transistor;

   The control electrode of the first transistor is connected to the PWM signal line, the first electrode of the first transistor is connected to a third voltage terminal, and the second electrode of the first transistor is connected to the organic light emitting transistor. A control electrode is connected, the first transistor is configured to be turned on when the pulse width modulation signal is at an active level, so as to apply a third voltage signal provided by a third voltage terminal to the control electrode of the organic light emitting transistor, and Controlling the organic light emitting transistor to stop emitting light.
6. The pixel circuit according to claim 1, wherein the first voltage terminal is connected to the second voltage terminal.
7. The pixel circuit according to claim 1, wherein the organic light emitting transistor is a bipolar organic light emitting transistor, and the second voltage terminal is configured to provide an AC voltage signal as the second voltage signal. .
8. The pixel circuit according to claim 7, wherein the second voltage terminal is configured to alternately provide a positive polarity voltage signal and a negative polarity voltage signal once every two consecutive frames in a frame period.
9. The pixel circuit according to claim 1, wherein the input sub-circuit includes a second transistor;

   A control electrode of the second transistor is connected to the gate line, a first electrode of the second transistor is connected to the data line, and a second electrode of the second transistor is connected to the light emission control sub-circuit.
10. The pixel circuit according to claim 1, wherein the light emission control sub-circuit includes a storage capacitor;

    A first pole of the storage capacitor is connected to the first voltage terminal, and a second pole of the storage capacitor is connected to a control electrode of the organic light emitting transistor and an output terminal of the input sub-circuit.
11. The pixel circuit according to any one of claims 1 to 8, wherein the second voltage terminal comprises a power supply voltage terminal; a second electrode of the organic light emitting transistor is connected to a common voltage terminal.
12. A driving method for a pixel circuit. The pixel circuit includes an input sub-circuit, a light-emitting control sub-circuit, and an organic light-emitting transistor. The driving method includes:

    During one frame time for the frame to be displayed:

    In the data writing phase, the input subcircuit writes the data signal provided by the data line into the light emission control subcircuit under the control of the gate scan signal provided by the gate line; and

    In the light emitting phase, the light emitting control sub-circuit drives the organic light emitting field effect tube to emit light according to the written data signal.
13. The driving method according to claim 12, wherein:

    The writing a data signal provided by a data line into a light emission control sub-circuit includes: maintaining a control corresponding to the data signal at a control electrode of the organic light-emitting transistor by supplying a first voltage signal to the light emission control sub-circuit. Pole voltage

    The controlling the light emitting of the organic light emitting transistor by the light emitting control sub-circuit according to the written data signal includes: providing a second voltage signal to a first pole of the organic light emitting transistor, and by corresponding to the data signal and the data signal. A driving current of a second voltage signal drives the organic light emitting transistor to emit light.
14. The driving method according to claim 12, wherein a voltage of the data signal is determined according to a gray scale to be displayed by the pixel circuit.
15. The driving method according to claim 12, wherein the one-frame time further includes a light-off period; the driving method further comprises:

    Controlling the organic light-emitting transistor to stop emitting light by applying a third voltage signal to a control electrode of the organic light-emitting transistor in the light-emitting off stage;

    The duration of the light-emitting phase is determined according to a gray level of a pixel or a sub-pixel of a frame to be displayed.
16. The driving method according to claim 15, wherein a voltage of the data signal is a gate voltage corresponding to a time when a light emission intensity of the organic light emitting transistor is maximum.
17. The driving method according to any one of claims 12 to 16, wherein the organic light emitting transistor is a bipolar organic light emitting transistor, and the second voltage signal is an alternating voltage signal.
18. The driving method according to claim 17, wherein a positive polarity voltage signal and a negative polarity voltage signal are alternately applied to a first pole of the organic light emitting transistor in a frame period in every two consecutive frame times.
19. A display device comprising the pixel circuit according to any one of claims 1-11.
20. A signal processor applied to the pixel circuit according to any one of claims 3-5, wherein the signal processor is configured to calculate a pulse width modulated signal according to a gray level to be displayed by the pixel circuit. Space ratio to generate a corresponding pulse width modulation signal and output it to the light-emitting cut-off sub-circuit in the pixel circuit.

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